How to Accurately Measure the Flow of Liquid or Gas

By Thomas Devaraj PhD, Senior Application Specialist, PTC

Ever wonder how to measure the flow of liquid or gas accurately?

More importantly, can you be certain that your measuring devices are performing accurately?

It is well known that in Formula 1 races, the fuel  is measured in kilograms rather than litres. This is because at different temperatures & pressures, fuel will have different volumes. For the same reason, jet fuel is usually measured  in a similar manner.

In my frequent encounters with oil industry professionals, I came across a similar problem that requires frequent checks and close monitoring to ensure that the highest degree of accuracy is maintained.

Gas pipelines are often shared for moving this valuable commodity around. Hence there is a good reason why the equipment that measures the flow of oil or gas needs to be accurate.  And with energy prices climbing ever higher, the margin for error is even smaller.

Even though the job of monitoring flow is performed by dedicated flow computers, it’s still crucial to check their accuracy based on operating conditions. Such an example using Mathcad to verify flow measurements is presented below.

Critical factors such as pressure, temperature, liquid and gas properties need to be taken in consideration to accurately determine mass flow rates.

Historically, such calculations were often done using a variety of different tools and  methods, Excel high on that list. The issues of limited transparency and lack of audit-ability of excel based approaches are ones I hear all too often.

Mathcad’s open and transparent document based approach to calculations makes the process of creating, updating, validating and re-using of calculations straightforward.

This is beneficial as often such projects involve collaborative efforts of engineers and consultants from different companies exchanging, auditing or reviewing complex calculations.

Ultimately, Mathcad provides an ideal platform for doing so, safely, efficiently and most importantly of working with confidence.

Finally, the financial implications of not performing the flow measurements accurately is clearly one to take note of and it emphasizes the importance of getting those calculations right!

Our thanks & credit for the worksheet content go to Smith Rea Energy Ltd, Aberdeen, UK